How to write the last question on the eighth page of mathematics in Qidong Middle School?
( 1)x+m； X-m.(2) Move one unit to the left; Move one unit to the right; Move left (-n); x-(-n)； Move to the right (-n); X+(-n)。 (Senior one last semester)
Solution: Because the vertical line is the shortest, we have to walk15m. (First semester)